Adjustable drafting instrument



Patented Sept. 11, 1928.

JWALTER IE. HOWDEN, OF EDWARDSVILLE, ILLINOIS.

^ADJUSTABLE"'DRAFT1NG INSTRUMENT.

Application led'Apri 12,1924. t S'eriaIiNo. 705,987.

This invention relates toan improvementym drafting instruments and pertains :morey particularly to that class of instruments i known as irregular curve'or arc forming devices. i

. Janother object of the invention is lin providing an improved `instrument for making or forming circles or curves which will in 1,

some instances supplant thel beam `form of compass now'm use.

A' further object of the invention is in pror viding' an improved adjustable curve form- "ing instrument Vwhich is without a centering s point.

Other and further objects will appear in the specification and be specifically pointed out in the appended claims, reference being had to the accompanying drawings, exemplifying the invention, and in which Figure 1 is a plan view of this improved adjustable drafting instrument.

Figure 2 is a fragmentary section taken approximately on the line 2-2 of Fig. 3.

Figure 3 is a vertical transverse section taken on the line 3--3 of Fig. 1.

Figure 4 is a plan view of the instrument on a reduced scale showing it `adjustadole to form a concave line.

Referring by numerals to the accompanying drawings, this improved instrument comprises a length of a round and resilient steel rod bent into an oblong shape and forming a pair of parallel legs 1 and 2 and end portions 3, the leg 2 being formed from the ends 4 of the resilient steel rod and having said ends bent so as to be in alinement with one another as shown in Fig. 2.

The ends 4 are each threaded as shown in Fig. 2, one end having a right hand thread 5 and the other end being` provided with a left hand thread 6, said threaded ends 5 'and 6 being normally held a distance apart, and for engagement. with said threads is an adjusting sleeve 7 having interior right hand threads 8 at one end and at the opposite end interior left handthreads 9, the threads 8 engaging the right hand threads 5 of the end 4, and the threads 9 engaging the left hand threads 6 of the other end 4 of the leg 2.

Loosely mounted over the ends 4 ofthe leg` 2 are a pair of bearings 10 of a holding` plate 11, each of said bearings having a tapered bore 12 and in which the small end of each bore is arranged outwardly.

This improved drafting instrument is adapted to take the place of the kwell known I beam-compassand inwaddition thereto is adapted tof be nse'dwmfmaking :irregular curves. V

In theuse of a beam-compass, itis oftenf inconvenient toA establish the: centering point thereof in instanceswhere"ascurved line is to be made on: a large radius, as it -is often necessary to describe aline upon a drawing sheet in such a position, thereon where-it is' neces-i saryto locate the centeringpoint of the beamcompass at a point removedfrom` the'drawinglboard'on which the drawing :sheet is.' located. With this improved. adjustable drafting instrument. no centering ypoint is neces-f sary as it can be located upon the drawing Y sheet in a. manner as is the ordinary irregular curve or scroll.

In the operation of this improved instrument, the outer edge 13 of the leg 1 serves as the marking or ruling edge and when it is desired to shape or adjust the leg 1 to a desired form or size of curve, the adjusting sleeve 7 is turned in a right hand direction in which the lengths 4 of the leg 2 will be drawn towards each other into the sleeve 7, thereby shortening the length of the leg 2 and dra-wing the inner end 14 of each of the end portions 3 inwardly thereby causing the leg 1 to be flexed outwardly as shown in both full and dotted lines in Fig. 1.

Nhen the desired formation of the leg 1 has been attained. the left hand of the operator is firmly held upon the holding plate 11 so that the draftsman can applya marking tool to the ruling edge 13 of the leg 1 and locate the desired curved formationupon the drawing sheet,

lf it is desired to produce a concave curve.

lthe adjusting sleeve 7 is turned in thedirection opposite to that which is was turned for causing the leg 1 to be forced outwardly as `shown in Fig. 1, said opposite turning of the sleeve 7 forcing the threaded ends 5 andG of the leg 2 away from each other within the sleeve 7 in which the inner end 14 of each of the end portions 3 will be forced loutwardly thereby causing the leg 1 to be flexed inwardly as shown in Fig. 4. rEhe tapered bore 12 provided in each of the bearings 10 of the holding plate 11 is for the purpose ofV preventing binding of said bearings upon the ends 4 of the leg 2 during fle-Ying of the leg` 2. Transversely disposed apertures 15 are provided in the adjusting sleeve 7 for the introduction of a manipulating tool 16 for making said sleeve turn with ease.

On account of the holding plate 11 being loosely mounted on the leg 2, said plate will readily adapt itself to flatly engage the drawingr sheet. l

It is obvious that the length of the round steel from which the legs 1 and 2 are comprised Will be resilient.

`To aid the flexing qualities of the legs 1 y and 2, notches 17, shown by dotted lines in Fig. 1, can be provided on one side of each of said legs. y

What I-claim'is :f 1. A drafting instrument made from a length of resilient material bent into an oblong shape having the ends of the material length disposed on one side ofthe oblong, and

drawing means connected to the endsof the material length for flexing a portion of the Vmaterial length.

2. A drafting instrument comprising a length 'of resilient steel rod bent into an ob'- long shape and forming a pair of paralleling l left hand threads of said end portions, and av holding plate swingably secured to the leg having the threaded ends.

4. A drafting instrument comprising a length of resilient steel rodbentinto an oblong shape and forming a pair of parallel legs, one

of lsaid legs being provided With alining spacedv apart endV portions, and drawing means V(zo-operable with each of said end portions adapted to flex both of said legs.

" W. E. HOWDEN. 

